Abstract: A contact pad array is provided. The contact pad array includes a plurality of first contact pads and a plurality of second contact pads. The first contact pads are arranged along the first direction. Each first contact pad includes two first lengthwise sides and two widthwise sides. The second contact pads are arranged along the first direction. Each second contact pad includes two second lengthwise sides and two second widthwise sides. The length of the second lengthwise side is substantially shorter than that of the first lengthwise side, and the width of the second widthwise side is substantially larger than that of the first widthwise side. The projection of the first widthwise side of each first contact pad on the first direction is completely within the projection of the second widthwise side of the corresponding second contact pad on the first direction.